In recent years, wearable devices have been under active development. Since a feature of wearable devices is that they are carried on one's body, many of them can conform to a curved surface of the body or be curved according to the movement of the body. Therefore, flexible secondary batteries for wearable devices have been also under development, like those for displays or other housings.
For example, Patent Document 1 discloses a sheet-like power storage device which can be curved or bent in at least one axis direction, and electronic devices including the power storage device.